Norrisanima miocaena , a new generic name and redescription of a stem balaenopteroid mysticete (Mammalia, Cetacea) from the Miocene of California

PeerJ

article

Matthew S. Leslie¹  Carlos Mauricio Peredo⁴  Nicholas D. Pyenson³ 

[1] Biology Department, Swarthmore College;Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution;Department of Paleobiology, National Museum of Natural History, Smithsonian Institution;Department of Earth and Environmental Science, University of Michigan;Department of Paleontology and Geology

关键词: Baleen whale;    Fossil calibration;    Rorqual;    Cetacean;    Evolution;    Balaenopteroidea;    Cetacea;    Fossil record;    Tortonian;    Monterey Formation;   

DOI  :  10.7717/peerj.7629

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Rorqual whales are among the most species rich group of baleen whales (or mysticetes) alive today, yet the monophyly of the traditional grouping (i.e., Balaenopteridae) remains unclear. Additionally, many fossil mysticetes putatively assigned to either Balaenopteridae or Balaenopteroidea may actually belong to stem lineages, although many of these fossil taxa suffer from inadequate descriptions of fragmentary skeletal material. Here we provide a redescription of the holotype of Megaptera miocaena, a fossil balaenopteroid from the Monterey Formation of California, which consists of a partial cranium, a fragment of the rostrum, a single vertebra, and both tympanoperiotics. Kellogg (1922) assigned the type specimen to the genus Megaptera Gray (1846), on the basis of its broad similarities to distinctive traits in the cranium of extant humpback whales (Megaptera novaeangliae (Borowski, 1781)). Subsequent phylogenetic analyses have found these two species as sister taxa in morphological datasets alone; the most recent systematic analyses using both molecular and morphological data sets place Megaptera miocaena as a stem balaenopteroid unrelated to humpback whales. Here, we redescribe the type specimen of Megaptera miocaena in the context of other fossil balaenopteroids discovered nearly a century since Kellogg’s original description and provide a morphological basis for discriminating it from Megaptera novaeangliae. We also provide a new generic name and recombine the taxon as Norrisanima miocaena, gen. nov., to reflect its phylogenetic position outside of crown Balaenopteroidea, unrelated to extant Megaptera. Lastly, we refine the stratigraphic age of Norrisanima miocaena, based on associated microfossils to a Tortonian age (7.6–7.3 Ma), which carries implications for understanding the origin of key features associated with feeding and body size evolution in this group of whales.

【 授权许可】

CC BY